Can't Send via POP unless Exchange VPN Connected

I use Outlook 2010 and have a POP account setup as default, I also have an Exchange account setup for a company I contract for and their Exchange has to connect via VPN. Default data store is set to the POP PST.

Problem is that unless i'm connected to the VPN I can't send mail from my POP account unless it's already in the address book or I'm replying to an email, the message I recieve says that exchange needs to be online

One possibility:
What is the name of the smtp server name assigned to the pop account.
-If it is your Exchange server that explains why the VPN needs to be connected
-If an ISP the local connection is probably a different ISP that the Exchange server site and the mail is blocked as it is seen as relaying. When the VPN is connected it is sent using the remote site's internet connection.
-If a 3rd party such as smtp.gmail.com it shouldn't be a problem

If either of the above is a problem, try using the local ISP's smtp server

The POP box is using it's own SMTP server, however, I've tried a different authenticated server which I would normally be able to use and the problem persists even on a different port.

The exchange box delivers mail to an OST and the POP to a separate PST, the PST is set to default for both mail and storage.

The reason I think this is to do with Outlook and the Exchange VPN is because it happens identically on two separate machines. Now sending mail can be flaky even with the VPN connected. I've deleted the POP account on one machine and recreated it but problem persists

I'm not sure it SHOULD work, you have setup an exchange account without using autodiscover service and a pop account on the same profile, is it possible for you to create a different profiles for those accounts?
I'm not 100% sure, so try to create the exchange account first and then add the pop account using this guide..it's for outlook 2007 but it's not very different.

In Outlook go to:

Tools > Account Settings > Email Tab.
Click New.
Select "Microsoft Exchange, POP3, IMAP, or HTTP"; click Next.
Check "Manually Configure Server Settings."; click Next.
Select "Internet Email"; click Next.
Enter information for the new email account. The account does not have to be an email account associated with our hosted service. For information on setting up accounts that are on our service please click POP or IMAP.
Once your information is entered correctly click Next.
You will see the "Congratulations" Screen; click Finish.
Go back to the "Account Settings" window.
Select "Data Files".
Verify your new account is saving to the proper location. If it is going to the same location as your Exchange profile (i.e. .ost file) all the email will be merged into your Exchange inbox. If it is going to a .pst file it will create its own mailbox folder.
If you need to create a new .pst file, click Add.
Select "Office Outlook Personal Folder File"; click OK.
You can change the file name if you wish and then press OK twice.
To associate the email account with the new .pst file go back to the "Email" Tab and select the account.
Press "Change Folder" and select the .pst folder location.
Click OK.
Click Close.

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